Belted track vehicles, including tractors, crawlers and wagons, have found application in the agricultural and construction industries because, among other advantages, they permit operators of agricultural machines to work the field in wetter conditions than are normally permitted with conventional rubber-tire tractors and wagons. Further, belted track vehicles have gained popularity because of their versatility in application. For example, they permit the machine to operate over the soil with reduced compaction of the soil even under normal conditions. This is true, not only in wet conditions, but under general conditions. The reason is that the weight and load of the vehicle are distributed over a larger contact area with the soil. This, in turn, not only reduces soil compaction, but permits an implement such as a grain wagon to carry a greater load while reducing the effects of wet conditions and soil compaction.
The current commercial practice regarding trailed-type vehicles is to use an endless belt or track with rubber guide lugs on the interior surface of the belt and extending inwardly, away from the ground-engaging side of the belt. A pair of pneumatic tire wheel assemblies are used on each end of the belt. These wheel assemblies engage the interior of the belt and, conventional tensioning mechanism straighten, align and tension the belt for use. Steel weldments with idler wheels are also used for the lower, ground-engaging section of the track, holding the track to the ground and distributing the load over a greater contact area.
Conventional pneumatic tire end wheel assemblies have a pair of spaced tires, and the lower idler wheels also include a pair of wheels which are spaced to allow clearance for the guide lugs of the belted tracks which maintain the track in the desired drive position, but are not used as drive elements.
Metal wheels have been suggested for the end wheel assemblies. One such wheel is disclosed in U.S. Pat. No. 5,190,363, which discloses a double-sided wheel having a central groove for receiving the guide lugs of the track, and a plurality of individual metal elements, in the form of elongated blocks, which are bolted to a fabricated metal wheel, and located on either side of the center groove to provide spaced, metal elements for engaging and supporting the interior of the track.
Another type of metal wheel for a belted track machine is disclosed in U.S. Pat. No. 5,769,512. In this embodiment, the entire steel wheel is cast as an integral unit, including a mounting hub, and first and second laterally extending arms for supporting spaced, cantilevered drive members which extend laterally outwardly of the hub and provide engagement members for the inner surface of the track, both for supporting the track and for driving the track. This type of drive wheel is expensive to manufacture since it requires machining of the entire belt engaging surfaces of the belt support elements, as well as machining the regions about the mounting bolts.
Prior art machines with pneumatic tires are sensitive to wheel alignment; and the air pressure of the tires in a paired assembly must be substantially equal in order to maintain the tire side wall and track guide lug pressures to a desired level. Any slight misalignment or unequal tire pressures will cause increased wear because of the friction and rubbing that is generated when the two rubber surfaces are in contact. From the standpoint of belt wear, it is more desirable to use metal for the end wheels since the coefficient of friction between metal and rubber is less than between rubber and rubber.
However, in the past, metal end wheels have been expensive to manufacture, especially the type of drive wheel disclosed in the above '512 patent wherein the entire wheel is cast integrally, and the traction elements are cantilevered. In the event of breakage or substantial damage to the cantilevered members, for example, the entire wheel must be replaced. Depending on the belt tension system of the vehicle, it may be difficult to replace metal wheels, as explained further below. Further, it is comparatively expensive to manufacture such integrally cast wheels and to handle and store them.